Skin cancer

 | March 1, 2007

Skin cancer

As a child, you probably never suspected that carefree days spent sunning and swimming could be a prelude to skin cancer. But those hours outdoors elevated your risk of developing skin cancer today. Experts estimate that by age 18, you've accumulated 85% of your lifetime exposure to ultraviolet rays.

Skin cancer is the most common cancer in the United States, diagnosed in more than one million Americans each year. Skin cancer causes about 10,000 deaths annually. Most are from melanoma, the most severe form of skin cancer, which has become far more common in recent decades as people have spent more leisure time outdoors. In most cases, skin cancer is not fatal, but it can be disfiguring. The good news is that with early detection and treatment, more than 90% of cases can be cured. The three major types of skin cancer (see Figure 3) are described below.

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Basal cell and squamous cell carcinomas

These two types of skin cancer are generally not life-threatening and are treated in similar ways.

The most benign form of skin cancer — and the least likely to spread to other parts of the body — is basal cell carcinoma. It's also the most common form, accounting for about 80% of cases. Basal cell carcinoma originates in basal cells located deep in the epidermis. The most common cause of this cancer is cumulative damage from sun exposure. A basal cell carcinoma may first appear as a pearly pimple or bump, a white- or yellow-colored scar, or a scaly red patch. Some basal cell cancers appear as an ulcer that won't heal. Basal cell cancer is very slow-growing, and will not develop into the potentially fatal melanoma. Sunscreens do not protect against basal cell carcinoma, according to one large long-term study on the subject. The reason is not yet understood.

Another 16% of skin cancers are squamous cell carcinomas. This form of cancer arises from flat, scale-like cells in the epidermis. Although squamous cell cancer usually isn't fatal, it can be life-threatening if it spreads to lymph nodes or internal organs. But even then, the cure rate is around 50%. Four times more men than women develop squamous cell carcinoma. It usually starts as a small, scaly bump and grows slowly until it resembles an ulcer or wart. Squamous cell cancers frequently occur on the face, lips, ears, or backs of the hands, and they too result from cumulative sun damage. Early detection is key to preventing the spread of squamous cell cancer. Like basal cell cancer, it will not develop into melanoma. Long-term sunscreen use reduces the risk of squamous cell carcinoma by about 35%, according to one large study.

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Treating basal cell and squamous cell cancers

Options for treating basal and squamous cell cancers are similar. Depending on the size and location of the tumor, both types can be surgically removed. The procedure involves removing the cancer and the tissue around it, called the margin, to ensure that all cancer cells have been removed. If they haven't, another procedure will be required. Most experienced dermatologists are quite skilled at estimating appropriate margins. The surgical scar can take several months to heal, especially if a tumor was removed from the face.

A technique called Mohs' micrographic surgery has the highest reported cure rate for basal and squamous cell cancers and is less likely than other forms of surgery to damage surrounding healthy skin. Named after Wisconsin surgeon Frederic Mohs, the technique consists of surgically removing cancerous tissue one layer at a time, and then immediately examining the specimen's entire surface area microscopically to see if there are any cancer cells at the outer edges of the tissue. If there are, more of the surrounding tissue can be removed. If not, only a small wound is left. This technique eliminates the guesswork from determining margins. Mohs' surgery is beneficial for cancers near the eyes and prominent areas of the face. In some cases, wounds from Mohs' surgery may not need surgical reconstruction.

Electrodesiccation and curettage — more commonly called scraping and burning — is a simple, effective treatment for very superficial basal and squamous cell carcinomas. The procedure uses a sharp scraping tool called a curette to scoop out the tumor and a small margin of surrounding skin. The area is then cauterized with an electric needle. The main drawback of this method is that there is no tissue left to examine to determine if all cancerous cells have been removed.

Other options include cryosurgery with liquid nitrogen, which is highly effective; laser surgery for superficial cancers; or treatment with fluorouracil or imiquimod cream, also for superficial cancers.

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Melanoma

Melanoma is a form of cancer that originates in the melanocytes, cells deep in the epidermis or in surface moles that produce pigment. Each year, malignant melanoma is diagnosed in about 45,000 Americans. Although it accounts for only 4% of cases of skin cancer, it's responsible for more than 75% of all skin cancer deaths. Without early detection and treatment, it can spread (metastasize) to the lymph nodes and internal organs. The lungs and liver are common targets when melanoma spreads. Its incidence has risen dramatically, from 1 in 5,000 in 1930, to about 1 in 65 in 2004.

Melanoma has several distinguishing characteristics that experts call the ABCDs of melanoma. These are asymmetry, meaning that each half of the growth looks different from the other; border irregularity, in which the edges are ragged or blurry; color that's unusual; and a diameter that exceeds 6 mm, about that of a pencil eraser. In general, experts recommend that any mole or growth that has enlarged or changed in any way be examined by a dermatologist.

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Treating melanoma

If a growth or mole looks like a melanoma, the doctor will take a biopsy to confirm the diagnosis. This entails removing either a sample of tissue or else the entire growth and some surrounding skin, and examining the tissue under a microscope to determine whether it's cancer. Depending on how deep a melanoma is, further tissue may have to be removed. In some cases, lymph nodes may be removed, too. A procedure called sentinel node biopsy is becoming more common to determine if the lymph node nearest the tumor contains any cancer cells. If it does, surgery to remove additional nodes right away can improve survival, according to a study published in 2006 in the New England Journal of Medicine .

In addition to surgery, standard treatments for melanoma include chemotherapy, radiation therapy, and biological therapy, which strengthens the immune system against the cancer. For reasons still not understood, chemotherapy generally helps only a small number of people with melanoma, and there is no standard treatment regimen.

Melanoma survival rates are good — 95% or higher if the tumor is less than 1 mm thick. But beyond 4 mm in thickness, the cure rate drops to 45%. As with most other forms of cancer, if the tumor has spread to distant organs, overall survival is lower, about 18%.

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Review Date: 2007-03-01

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